City of Punta Gorda Adaptation Plan Southwest Florida Regional ...

Rip-rap and rock lining,

Rip-rap and rock lining, random, broken stone, 300 lb. average, dumped Ton 73.50 Gabion boxes, galvanized steel mesh mats or boxes, stone filled, 6" deep S.Y. 59.50 Gabion boxes, galvanized steel mesh mats or boxes, stone filled, 9" deep S.Y. 84.00 Gabion boxes, galvanized steel mesh mats or boxes, stone filled, 12" deep S.Y. 92.00 Gabion boxes, galvanized steel mesh mats or boxes, stone filled, 18" deep S.Y. 133.00 Gabion boxes, galvanized steel mesh mats or boxes, stone filled, 36" deep S.Y. 201.00 Table 54: 2009 Construction Bare Unit Costs for coastal armoring. (LF = linear foot; CY = cubic yard; SY = square yard) Source: SFWMD 2008 The United States Geological Survey (USGS) has created an index to rate the vulnerability of U.S. shoreline to sea level rise, taking into consideration tides and erosion, as well as elevation (USGS 2000). According to their assessment, out of 4,000 miles of total Florida shoreline, 1,250 miles are in the ―high‖ vulnerability category and 460 miles are in the ―very high‖ category. If just these 1,700 miles of shoreline were protected with seawalls, and construction costs averaged $1,000 per linear foot (or a bit over $5 million per mile), the total cost would be just under $9 billion. The 4,000 total miles of shoreline assumed by USGS, however, do not take into account Florida‘s many channels and inlets, which make the actual coastline much longer. (Conversely, other estimates of the length ofFlorida‘s coastline range down to 1,350 or fewer miles; the varying estimates reflect the different resolutions at which the measurements are made.). The actual coastline length, when these features are accounted for, is 22,000 miles (Stanton and Ackerman 2007)If seawalls were needed for 42 percent ofFlorida‘s actual coastline (the share of very high and high vulnerability coastline under the USGS definition), or 9,200 miles, the cost would be $49 billion. In other words, constructing seawalls sufficient for statewide protection would be an engineering mega project, several times the size of the long-term Everglades restoration effort (Stanton and Ackerman 2007). Yet another approach involves beach nourishment, bringing in sand as needed to replenish and raise coastal beaches (which as noted above can have major environmental impacts). A largescale analysis of the costs of protecting the U.S. coastline from sea level rise, conducted by USEPA in 1989, relied heavily on restoring and building up beaches (Titus et al. 1991). The study projected that most of the sand would need to be dredged up from more than five miles offshore. It estimated the cost of sand to protect Florida against 39 inches of sea level rise (a level reached in 2087 in the worst case) would be between $6 billion and $30 billion in 2006 dollars, depending on assumptions about the quantity and cost of sand. As with statewide seawall construction, beach nourishment on this scale would be a mammoth engineering project, with uncertain environmental impacts of its own. In short, while adaptation, including measures to protect the most valuable real estate, will undoubtedly reduce sea level rise damages, there is no single, believable technology or strategy for protecting the vulnerable areas throughout the state (Stanton and Ackerman 2007). AdaptationPlan Page 214